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The flexibility in design offered by advanced additive manufacturing technologies makes these processes more and more attractive for automotive and aircraft applications and, also, for the production of safety relevant metal components. The high strength, thermally resistant nickel-based alloy Inconel®718 is widely used by the aircraft industry and its low level of machinability makes it an optimal candidate for AM technologies. The challenge, together with improving the process, is now to build the path that will bring AM technologies from rapid prototyping to series production. Therefore, it is essential to investigate additively manufactured materials and the effect that subsequent processing, such as, for example surface preparation, has on their properties. Furthermore, while the static properties of additively manufactured Inconel®718 have already been investigated, this work aims to describe its cyclic stress-strain behavior, which can be used for fatigue assessment.

Additive manufacturing offers new options for lightweight design for safety parts under cyclic loading conditions. In order to utilize all advantages and exploit the full potential of additive manufactured parts, the main impact factors on the cyclic material behavior not only have to be identified and quantified but also prepared for the numerical fatigue assessment. This means in case of the AlSi10Mg aluminum alloy to consider influences related to the exposure strategy, heat treatment, microstructure, support structures and the surface conditions, as well as the influence of the load history and finally the interaction of these influences in order to perform a high quality fatigue assessment. Due to these reasons, and with respect to the numerical effort, the cyclic material behavior of additively manufactured AlSi10Mg produced by selective laser melting will be discussed.

Manganese sulfides (MnS) are nonmetallic, ductile inclusions with high melting temperature (1610 °C) which improve the machinability and retard the grain growth in steels, in addition of contributing to avoid cracking during hot working. In this paper, the effect of manganese sulfides on the fatigue life of the vanadium micro-alloyed forging steel 38MnVS6 is discussed. Force-controlled fatigue tests are performed on small sized specimens until the crack occurs. The fatigue life of the forged material, presented by Wöhler curves, is considerably reduced at high levels of the nominal stress amplitude compared to the wrought material. Moreover, it is evident that the presence of longer and thinner particles of MnS reduces the scatter band of Wöhler curves and decreases the fatigue strength of the material. This paper presents a first attempt to find a relation between the shape and content of manganese sulfides due to the forging process and the fatigue life of the material.

The cyclic material behavior is investigated, by strain-controlled testing, of 8 mm thick sheet metal specimens and butt joints, manufactured by manual gas metal arc welding (GMAW). The materials used in this investigation are the high-strength structural steels S960QL, S960M and S1100QL. Trilinear strain-life curves and cyclic stress-strain curves have been derived for the base material and the as-welded state of each steel grade. Due to the cyclic softening in combination with a high load level at the initial load cycle, the cyclic stress-strain curve cannot be applied directly for a fatigue assessment of welded structures. Therefore, the transient effects have been analyzed in order to describe the time-variant material behavior in a more detailed manner. This should be the basis for the enhancement of the fatigue life estimation.